Cobalt-based jewelry article

ABSTRACT

An article of jewelry and method of producing an article of jewelry, comprising providing a substrate made of a biocompatible medical grade cobalt-based alloy that includes cobalt, chromium and molybdenum. The cobalt-based alloy substrate is formed into a desired shape of the article of jewelry.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/220,995 filed Jun. 26, 2009, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

This disclosure relates generally to jewelry, and, more specifically, to jewelry fashioned from biocompatible medical grade cobalt-based alloys.

2. Description of Related Art

Cobalt is generally considered to be a poor material with which to make jewelry. Cobalt is a confirmed carcinogen, is hazardous to ingest, and causes irritation when it comes in contact with human skin. Alloys that include cobalt typically develop oxidation, which cannot be removed.

Not all cobalt alloys, however, exhibit these poor characteristics. Cobalt-based super alloys have been used to make blades for gas turbines and aircraft engines. Similarly, cobalt-based alloys have been used for biomedical applications. For instance, cobalt-chromium-molybdenum (Co—Cr—Mo) alloys, such as Co-28Cr-6Mo, have been used to make orthopedic, dental, neurological, and cardiovascular implant devices. Such alloys are considered excellent materials for use as medical implants because of their biocompatibility and resistance to the corrosive conditions existing inside and on the human body.

BRIEF SUMMARY

In one aspect of this disclosure, jewelry and accessories made of a biocompatible medical grade cobalt-based alloy are disclosed. The cobalt-based alloy comprises cobalt, chromium and molybdenum. The biocompatible medical grade cobalt-based alloy provides a unique combination of strength, hardness, ductility, corrosion resistance, and is unusually resistant to scratching or wear, while at the same time providing a pleasing aesthetic appearance.

In another aspect of this disclosure, a method of producing an article of jewelry or accessory is disclosed. The method comprises providing a substrate made of a biocompatible medical grade cobalt-based alloy consisting essentially of cobalt, chromium and molybdenum. The cobalt-based alloy substrate is formed into a desired shape of the article of jewelry.

The foregoing has outlined rather generally the features and technical advantages of one or more embodiments of this disclosure in order that the following detailed description may be better understood. Additional features and advantages of this disclosure will be described hereinafter, which may form the subject of the claims of this application.

BRIEF DESCRIPTION OF THE DRAWINGS

This disclosure is further described in the detailed description that follows, with reference to the drawings, in which:

FIG. 1 is a perspective view of an illustrative article of jewelry made from a biocompatible cobalt-based alloy in accordance with this disclosure.

DETAILED DESCRIPTION

This application discloses the use of biocompatible cobalt-based alloys as a base material for the creation of jewelry articles (e.g., rings, bands, earrings, chains, necklaces, bracelets, etc.) and accessories (e.g., belt buckles, cufflinks, money clips, shirt studs, etc.). An illustrative article of jewelry 100 made from a biocompatible cobalt-based alloy in accordance with this disclosure is illustrated in FIG. 1. The article of jewelry 100 may, for example, be formed into an annular body or band 110 having an opening through which a body part such as a finger may be inserted so that the article of jewelry may be worn by the user.

Medical grade cobalt-based alloys, such as Co—Cr—Mo alloys, are highly biocompatible with the human body, contrary to previous experience with cobalt and other cobalt alloys. Medical grade cobalt-based alloys are also very strong and hard, but are not brittle like other materials such as tungsten or ceramic. Furthermore, medical grade cobalt-based alloys do not tarnish, and are highly wear and scratch resistant. Finally, medical grade cobalt-based alloys are extremely white, like platinum, and therefore provide an attractive material from which to make jewelry and accessories.

There are many different medical grade cobalt-based alloys available on the market. Any such alloy exhibiting characteristics beneficial to the jewelry manufacturer may be used. The medical grade cobalt-based alloy for creating jewelry articles and accessories preferably includes about 26-30% chromium (Cr), about 5-7% molybdenum (Mo), and about 57-70% cobalt (Co). In addition, the medical grade cobalt-based alloy preferably includes not more than about 1% manganese (Mn), not more than about 1% silicon (Si), and not more than about 1% nickel (Ni). Further, the medical grade cobalt-based alloy preferably includes not more than about 0.25% nitrogen (N), not more than about 1.5% iron (Fe), and not more than about 0.35% carbon (C).

A preferred medical grade cobalt-based alloy is BioDur® Carpenter CCM® Alloy, or the Micro-Melt® BioDur® Carpenter CCM® Alloy, both manufactured by Carpenter™ Corporation and disclosed in U.S. Pat. No. 5,462,575. These alloys may be prepared initially as a powdered charge consisting of about 26-30% chromium (Cr), about 5-7% molybdenum (Mo), about 1% max. manganese (Mn), about 1% max. silicon (Si), about 1% max. nickel (Ni), about 0.75% max. iron (Fe), about 0.25% max. nitrogen (N), about 0.14% max. carbon (C), with the balance of the mixture (58.86-69%) consisting of cobalt (Co).

Another medical grade cobalt-based alloy is designated as ASTM F75 (Standard Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants). ASTM F75 alloy consists of about 27-30% chromium (Cr), about 5-7% molybdenum (Mo), about 1% max. manganese (Mn), about 1% max. silicon (Si), about 1% max. nickel (Ni), about 0.75% max. iron (Fe), about 0.35% max. carbon (C), with the balance of the mixture (58.9-69.5%) consisting of cobalt (Co). Examples of commercially available cobalt-based alloys meeting ASTM F75 include Vitallium (Howmedica, Inc.), Haynes-Stellite 21 (HS21) (Cabot Corp.), Protasul-2 (Sulzer AG) and Micrograin-Zimaloy (Zimmer USA).

Another medical grade cobalt-based alloy is designated as ASTM F799 (Standard Specification for Cobalt-28Chromium-6 Molybdenum Alloy Forgings for Surgical Implants). ASTM F799 alloy consists of about 26-30% chromium (Cr), about 5-7% molybdenum (Mo), about 1% max. manganese (Mn), about 1% max. silicon (Si), about 1% max. nickel (Ni), about 1.5% max. iron (Fe), about 0.35% max. carbon (C), about 0.25% max. nitrogen (N), with the balance of the mixture (58-69%) consisting of cobalt (Co).

Another medical grade cobalt-based alloy is designated as ASTM F1537 (Standard Specification for Wrought Cobalt-28Chromium-6 Molybdenum Alloys for Surgical Implants). ASTM F1537 (Alloy 1 (Low Carbon) Forged) consists of about 26-30% chromium (Cr), about 5-7% molybdenum (Mo), about 1% max. manganese (Mn), about 1% max. silicon (Si), about 1% max. nickel (Ni), about 0.75% max. iron (Fe), about 0.14% max. carbon (C), about 0.25% max. nitrogen (N), with the balance of the mixture (58.86-69%) consisting of cobalt (Co).

ASTM F1537 (Alloy 2 (High Carbon) Forged) consists of about 26-30% chromium (Cr), about 5-7% molybdenum (Mo), about 1% max. manganese (Mn), about 1% max. silicon (Si), about 1% max. nickel (Ni), about 0.75% max. iron (Fe), about 0.15-0.35% max. carbon (C), about 0.25% max. nitrogen (N), with the balance of the mixture (58.65-68.85%) consisting of cobalt (Co).

ASTM F1537 (Alloy 3 (Dispersion Strengthened) Forged) consists of about 26-30% chromium (Cr), about 5-7% molybdenum (Mo), about 1% max. manganese (Mn), about 1% max. silicon (Si), about 1% max. nickel (Ni), about 0.75% max. iron (Fe), about 0.14% max. carbon (C), about 0.25% max. nitrogen (N), about 0.3-1.0% max. aluminum (Al), about 0.03-0.2% lanthanum (La), with the balance of the mixture (57.66-68.67%) consisting of cobalt (Co).

The table below summarizes the approximate range of constituents by weight percentage (wt. %) in each of the above-mentioned illustrative medical grade cobalt-based alloys:

Micro-Melt ® BioDur ® BioDur ® Carpenter Carpenter ASTM ASTM ASTM F 1537 ASTM F 1537 ASTM F 1537 CCM ® Alloy CCM ® Alloy F75 F799 (Alloy 1) (Alloy 2) (Alloy 3) (wt. %) (wt. %) (wt. %) (wt. %) (wt. %) (wt. %) (wt. %) Cr 26-30 26-30 27-30 26-30 26-30 26-30 26-30 Mo 5-7 5-7 5-7 5-7 5-7 5-7 5-7 C 0.10 max. 0.14 max. 0.35 max. 0.35 max. 0.14 max. 0.15-0.35 0.14 max. Mn 1.00 max. 1.00 max. 1.00 max. 1.00 max. 1.00 max. 1.00 max. 1.00 max. Si 1.00 max. 1.00 max. 1.00 max. 1.00 max. 1.00 max. 1.00 max. 1.00 max. Ni 1.00 max. 1.00 max. 1.00 max. 1.00 max. 1.00 max. 1.00 max. 1.00 max. N 0.25 max. 0.25 max. 0.25 max. 0.25 max. 0.25 max. 0.25 max. Fe 0.75 max. 0.75 max. 0.75 max. 1.50 max. 0.75 max. 0.75 max. 0.75 max. Al 0.3-1.0 La 0.03-0.2  Co Balance Balance Balance Balance Balance Balance Balance (58.9-69)   (58.86-69)   (58.9-69.5) (58-69) (58.86-69)   (58.65-68.85) (57.66-68.67)

It is understood that variations of the above-described cobalt-based alloys may be used to form jewelry and accessories. For instance, cobalt-based alloys other than biocompatible medical-grade cobalt-based alloys may be used to make jewelry and accessory items so long as the material does not irritate or otherwise cause an adverse reaction when coming into contact with the skin of a person wearing the jewelry and/or accessory item.

While medical grade cobalt-based alloys are preferred, other cobalt-based alloys may be utilized that include nickel (Ni) in an amount that exceeds 1%. For instance, the cobalt-based alloy may include nickel (Ni) that exceeds 5%. It is, however, preferred that the nickel (Ni) content of the cobalt-based alloy not be more than about 5%, more preferably not more than about 3%, and most preferably not more than about 1% nickel (Ni).

Forming the actual jewelry article or accessory from a medical grade cobalt-based alloy presents new challenges. The qualities that make medical grade cobalt-based alloys so attractive also create difficulties in manufacturing. The material is very strong and relatively hard, making it difficult to fashion into jewelry. For this reason, creating jewelry and accessories out of medical grade cobalt-based alloys may involve technology and manufacturing techniques used in the biomedical and aerospace industries, but not typically utilized by jewelers in the jewelry industry. Alternatively, conventional manufacturing techniques may also be substantially modified to accommodate difficulties in working with medical grade cobalt-based alloys.

Jewelry and accessories may be formed from medical grade cobalt-based alloys by, for example, machining, stamping, casting, injection molding, water jet cutting, or manipulation processes. Hot and cold forging (in open and closed dies), die striking, hot forming and spinning are also viable methods for manufacturing jewelry and accessory items from medical grade cobalt-based alloys. Other production methods, including chemical etching, may be used as appropriate.

Medical grade cobalt-based alloys may be ground, sawed, drilled, stamped, sheered, sanded or cut just like any other metal. The hardness and strength of the cobalt-based alloy can adversely affect tool life compared to manipulation of softer, more common metals typically utilized to make jewelry. In response, harder or more resilient materials are preferably used in the cutter machinery to compensate. Additionally, it may be beneficial to alter the cutting speed or cutting angle. Coolant is preferably used when machining the cobalt-based alloy.

For example, wrought medical grade cobalt-based alloy, such as BioDur® Carpenter CCM® Alloy, in bar stock or tubing form may be machined to form a desired shape of the jewelry or accessory item. This may be done, for example, by machining the medical grade cobalt-based alloy bar stock or substrate on a CNC machine, which is preprogrammed with the desired shape of the jewelry or accessory item. Alternatively, the bar stock may be formed into the desired shape using a conventional lathe and/or milling machine. Once formed into the desired shape, a desired profile may be cut on the outside of the formed jewelry or accessory item. The machined jewelry or accessory item may be deburred on a milling machine or the like.

Finishing may be accomplished by a variety of methods, including chemical finishing, mass finishing and hand finishing. Combinations of these finishing methods may be utilized in a variety of ways to achieve alternative finishes. The finishing process may serve to burnish, deburr, clean, radius, de-flash, descale, polish, brighten, surface harden and/or prepare parts for further processing.

As an alternative, powder metallurgy may be utilized to form the jewelry or accessory item in, for example, a casting process. A powdered medical grade cobalt-based alloy, such as Micro-Melt® BioDur® Carpenter CCM® Alloy, may be combined with a resin based mix. The combination is preferably placed in a mold, and then subjected to intense pressure and heat. The resin may then be removed by burning, and the final dense compact is preferably left to cool and shrink to form the desired shape of the jewelry or accessory item. This process allows for the manufacture of clean and raw products that need little in the way of post formation processing and finishing. Careful control should be exercised over the proportions of powder relative to resin in the mixture, as this ratio affects final shrinkage and finished part dimensions of the product during cooling.

Alternatively, the powdered medical grade cobalt-based alloy may be placed within a sealed canister, which may be subjected to heat and vacuum, and then consolidated at an elevated temperature and pressure to form a dense or consolidated alloy powder, which may then be machined or otherwise formed into the desired shape of the jewelry or accessory item.

Once formed, secondary operations may also be performed on the jewelry and accessories made from medical grade cobalt-based alloys. For example, precious metals and other materials (e.g., diamonds, gems, stones, carbon fiber, leather, wood, etc.) may be inlayed into the formed jewelry. For instance, a gold inlay may be added to the formed product by cutting a v-channel or any other type of groove into the cobalt-based alloy using a milling machine and/or lathe. The gold may be pressed into the v-channel and locked in place with a dovetail type joint or the like. The inlay may then be reprofiled to level it with the surrounding cobalt-based alloy material.

Having described and illustrated the principles of this application by reference to one or more preferred embodiments, it should be apparent that the preferred embodiment(s) may be modified in arrangement and detail without departing from the principles disclosed herein and that it is intended that the application be construed as including all such modifications and variations insofar as they come within the spirit and scope of the subject matter disclosed herein. 

1. An article of jewelry, comprising at least one jewelry component made of a cobalt-based alloy that comprises cobalt, chromium and molybdenum.
 2. The article of jewelry according to claim 1, wherein the cobalt-based alloy is a biocompatible medical grade cobalt-based alloy.
 3. The article of jewelry according to claim 2, wherein the cobalt-based alloy consists essentially of about 26-30% chromium, about 5-7% molybdenum, about 1% max. manganese, about 1% max. silicon, about 1% max. nickel, about 0.75% max. iron, about 0.25% max. nitrogen, about 0.14% max. carbon, and the balance consisting of cobalt.
 4. The article of jewelry according to claim 3, wherein the cobalt-based alloy contains not more than about 0.10% carbon.
 5. The article of jewelry according to claim 1, wherein the cobalt-based alloy comprises about 26-30% chromium, about 5-7% molybdenum, and about 57-70% cobalt.
 6. The article of jewelry according to claim 5, wherein the cobalt-based alloy further comprises not more than about 5% nickel.
 7. The article of jewelry according to claim 6, wherein the cobalt-based alloy further comprises not more than about 3% nickel.
 8. The article of jewelry according to claim 7, wherein the cobalt-based alloy further comprises not more than about 1% nickel.
 9. The article of jewelry according to claim 8, wherein the cobalt-based alloy further comprises not more than about 1% manganese and not more than about 1% silicon.
 10. The article of jewelry according to claim 9, wherein the cobalt-based alloy further comprises not more than about 0.25% nitrogen.
 11. The article of jewelry according to claim 9, wherein the cobalt-based alloy further comprises not more than about 1.5% iron.
 12. The article of jewelry according to claim 11, wherein the cobalt-based alloy further comprises not more than about 0.75% iron.
 13. The article of jewelry according to claim 9, wherein the cobalt-based alloy further comprises not more than about 0.35% carbon.
 14. The article of jewelry according to claim 13, wherein the cobalt-based alloy further comprises about 0.15-0.35% carbon.
 15. The article of jewelry according to claim 13, wherein the cobalt-based alloy further comprises not more than about 0.14% carbon.
 16. The article of jewelry according to claim 15, wherein the cobalt-based alloy further comprises not more than about 0.10% carbon.
 17. The article of jewelry according to claim 1, wherein the article of jewelry is selected from the group consisting of a ring, band, earring, chain, necklace, bracelet, belt buckle, cufflink, money clip and shirt stud.
 18. A method of producing an article of jewelry, comprising: providing a substrate made of a cobalt-based alloy comprising cobalt, chromium and molybdenum; and forming the cobalt-based alloy substrate into a desired shape of the article of jewelry.
 19. The method according to claim 18, wherein the cobalt-based alloy is a biocompatible medical grade cobalt-based alloy.
 20. The method according to claim 19, wherein the cobalt-based alloy consists essentially of about 26-30% chromium, about 5-7% molybdenum, about 1% max. manganese, about 1% max. silicon, about 1% max. nickel, about 0.75% max. iron, about 0.25% max. nitrogen, about 0.14% max. carbon, and the balance consisting of cobalt.
 21. The method according to claim 20, wherein the cobalt-based alloy contains not more than about 0.10% carbon.
 22. The method according to claim 18, wherein the cobalt-based alloy comprises about 26-30% chromium, about 5-7% molybdenum, and about 57-70% cobalt.
 23. The method according to claim 22, wherein the cobalt-based alloy further comprises not more than about 5% nickel.
 24. The article of jewelry according to claim 23, wherein the cobalt-based alloy further comprises not more than about 3% nickel.
 25. The article of jewelry according to claim 24, wherein the cobalt-based alloy further comprises not more than about 1% nickel.
 26. The method according to claim 25, wherein the cobalt-based alloy further comprises not more than about 1% manganese and not more than about 1% silicon.
 27. The method according to claim 26, wherein the cobalt-based alloy further comprises not more than about 0.25% nitrogen.
 28. The method according to claim 26, wherein the cobalt-based alloy further comprises not more than about 1.5% iron.
 29. The method according to claim 28, wherein the cobalt-based alloy further comprises not more than about 0.75% iron.
 30. The method according to claim 26, wherein the cobalt-based alloy further comprises not more than about 0.35% carbon.
 31. The method according to claim 30, wherein the cobalt-based alloy further comprises about 0.15-0.35% carbon.
 32. The method according to claim 30, wherein the cobalt-based alloy further comprises not more than about 0.14% carbon.
 33. The method according to claim 32, wherein the cobalt-based alloy further comprises not more than about 0.10% carbon.
 34. An article of jewelry formed by the method of claim
 18. 35. The method according to claim 34, wherein the article of jewelry is selected from the group consisting of a ring, band, earring, chain, necklace, bracelet, belt buckle, cufflink, money clip and shirt stud. 